There's no explanation for what Kuzan is doing to his own mentor to please low lifes other than achieving greater objectives.
Kuzan legit sees a monstrous D. chad energy lain dormant inside Teach, and he wants to activate it against something that he can't challenge alone, like Imu and the elders.
Like an "Enemy Mine" situation or something, using the lesser of 2 evils to take down a greater one or something. Enemy of my enemy is my friend?
Makes a lot more sense. He could still be pulling an Itachi sort of stunt but following his own agenda and no actual allegiances instead of the blatantly ruined/disproved Kuzan in Sword theory now too lol. I don't think he's working with the Revolutionaries either but it would be hilariously ironic if he was lol. Dragon secretly letting out his anger towards Garp indirectly through Kuzan lol.
He probably does feel Blackbeard is the only one who can take down Imu and kill them especially, be willing to. He probably thinks Akainu is too much of a "loyal dog" and they blatantly couldn't come to an agreement during their fight ofc. He's probably seeing the Gorosei's true natures as well, as an Admiral and especially being considered for FA too.
Kuzan's whole attitude does come across as he's seen some fucked up shit he can't expose/talk about yet and he's gone rogue to try and deal with it in his own secretive way.